1. Field of the Invention
This invention relates to a styrene-acrylonitrile resin composition having a good parting property.
More particularly, this invention relates to a resin composition having an excellent parting property, which is formed by blending in a styrene-acrylonitrile resin, an .alpha.-olefin epoxide of the formula ##EQU2## wherein R and R' is hydrogen or straight-chain alkyl, with the proviso that the sum of the carbon atoms in R plus R' is 8 to 13, preferably 10 to 12.
2. Description of the Prior Art
Improvement of the flowability of plastics during molding and/or prevention of sticking or adhesion of plastics on processing machine parts is generally accomplished by adding parting agents to the plastics. It is known that various parting agents are added to styrene-acrylonitrile resins for the above purposes. More specifically, silicone resins, higher fatty acids and their metal salts, higher fatty acid amides, montan wax and the like are incorporated into styrene-acrylonitrile resins as internal release agents during the molding step. However, because of their low compatibility with styrene-acrylonitrile resins, these conventional parting agents reduce the transparency of styrene-acrylonitrile resins and sometimes cause turbidity or whitening of the resin compositions. Further, when molding compositions containing these conventional parting agents are present in a molding machine for a long time, the thermal stability of the resin is degraded. Also, surging is caused to occur in the molding machines when such agents are present in relatively large amounts. Thus, conventional parting agents for styrene-acrylonitrile resins give rise to problems which must be solved. Moreover, as is illustrated in the Example given below, when the molded article to be produced has a constricted portion of relatively small cross-sectional size, because the pressure imposed on this portion is locally increased during the molding step, the parting or releasing property of this constricted portion after the molding step is extremely bad. Frequently it is necessary to separate the molded article from the mold by force. Accordingly, in some extreme cases, this portion becomes bent and broken or is made opaque.